1. Field of the Invention
This invention resides in the field of high-vacuum valves and the structural features that are designed to prolong the useful life of such a valve and to eliminate or reduce the risk of introducing debris into procedures where such valves are used.
2. Description of the Prior Art
High-vacuum valves are critical equipment in a wide variety of procedures, ranging from analytical procedures to manufacturing processes. Particle physics experiments, x-ray tomography procedures, manufacturing processes for high-precision electronic components, and procedures involving the application of coatings by chemical vapor deposition are just examples of the many applications where high-vacuum valves are used. High-vacuum valves are particularly critical in semiconductor fabrication, where both high vacuum and a scrupulously clean environment are essential in achieving high-quality products. Other examples are flat panel displays, thin film magnetic switches, and optical switches. In procedures where a high-vacuum valve is opened and closed repeatedly, a valve that remains clean and performs reliably is even more critical since the opening and closing can cause wear and deterioration of the valve. In semiconductor fabrication, for example, high-vacuum valves are opened and closed repeatedly as semiconductor wafers are conveyed from the ambient environment to a high-vacuum chamber and back again.
High-vacuum valves of the prior art typically contain several moving parts that encounter friction and suffer abrasion and other types of wear. With extended use of these valves, the repeated abrasion produces debris, including metal debris that is microscopic in size. The presence of debris in a valve inevitably lowers the yield of acceptable products produced from equipment in which the valve is used. The moving parts often cause vibration as well, which further adds to the risk of low product quality. The need to discard products that do not meet specifications and to replace worn valves adds considerably to the manufacturing costs.
Another consideration that often arises in high-vacuum valves is the need to maintain the vacuum when a power failure or other event occurs that interferes with the actuation of the valve. An external force is typically needed to maintain the seal integrity when such an event occurs. The orientation of a high-vacuum valve is often a compromise between maintaining the seal integrity under these circumstances and prolonging the life of the valve. This complicates the construction of the valve.